- Mount Rainier earthquake swarm of July, 2025
- Bob Crosson has passed away
- Tonasket Earthquake Swarm or Aftershock Sequence?
- M4.5 Earthquake at Orcas Island, Washington, March 3rd, 2025
- 2024 PNSN Earthquake Catalog
- Rumblings: Preparing for Cascadia - Documentary Screening and Discussion
- 'N Yo' Seismic Network: Marshawn Lynch Shakes the PNSN!
- Swarms in Eastern Washington: are there fewer now than in the past?
- New Algorithm GFAST Enhances the ShakeAlert Earthquake Early Warning System
- Don't Get Scared, Get Prepared!
- 2025 6
- 2024 3
- 2023 5
- 2022 9
- 2021 16
- 2020 5
- 2019 10
- 2018 11
- 2017 10
- 2016 16
- 2015 11
- 2014 16
- 2013 14
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2012
48
- December 1
- November 2
- October 3
- September 1
- August 3
- July 2
- June 4
- May 4
- April 2
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March
8
- The wech-o-meter takes over all of Cascadia
- Keystone Cops: Italy prosecutes seismologists for failure to predict deadly quake
- UFOs in eastern Washington? No, rather UTEs (Unidentified Terrestrial Events)
- New Sodo Seattle Liquefaction Array Installed
- Why we should constantly watch the deformation of the seafloor
- Mystery chirp near Newberry Volcano
- Planting seismographs causes earthquakes? or maybe ice-quakes?
- Tunneling rumbles south under Capitol Hill
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February
7
- 15 years of mostly silent magma inflation near Three Sisters, Oregon
- Mount Hood earthquake swarm of Feb 23, 2012
- Web glitches: duplicate (and even triplicate!) earthquakes
- How earthquake magnitude scales work
- Mine blast masquerades as volcanic tremor
- The Spokane Swarm about 10 years ago
- Another hum around Mount St. Helens
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January
11
- Slow slip: A new kind of earthquake under our feet
- PNSN and social media
- 3am M3.4 earthquake in St. Helens Seismic Zone
- The wrong kind of volcano noise
- Fast chatter on Rainier an hour ago
- Can slush-mageddon trigger earthquakes?
- Rainier Repeating Earthquakes Update and Comparison with Weather Patterns
- 22-minutes drumbeat icequakes(?)
- Mount Rainier popping away
- Repeating Earthquakes on Mount Rainier - are glaciers the culprit?
- Debunking another SEC football myth by the PAC-12
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2011
17
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December
13
- One year ago, Seattle Seahawks 12th Man Earthquake
- The odds this year of a megaquake on the Pacific Northwest coast
- Is the plague of great earthquakes this decade a sign of increased danger?
- Nile Valley landslide talks to PNSN seismologists
- Good vs evil in central US earthquake hazard analysis
- Why does a volcano scream?
- Predicting big quakes from patterns of little ones
- 1-hour warning for Japanese M9 earthquake?
- Sound Transit train under Interlaken keeps a rollin'
- Invisible changes under the hood at the PNSN
- Sound Transit Tunneling Noise
- "Visionary" toads
- Earthquake early warning in the PNW
- November 1
- March 2
- February 1
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December
13
December 2017 Oregon Tremor Event
Over the past 9-10 days, it appears that tremor in central Oregon has picked up (Figure 1). The last slow slip and tremor event was in February 2016, 22 months ago.
Figure 1
Figure 1. Age progression of tremor in central Oregon for the past 9 days. Earliest tremor locations start from 12/5/2017 and propagate roughly outward, clustering near Salem and Roseburg. Last update was December 14, 2017.
Tremor is the release of seismic noise from slow slip along the interface of the Juan de Fuca and North American plates and lasts for several weeks to months. This process is known as Episodic Tremor and Slip (ETS). Slow slip happens down-dip of the locked zone (Figure 2). The locked zone is where tectonic stress builds up until it releases in a great earthquake or megaquake. The recurrence interval of slow slip and tremor varies at different regions along the Cascadia Subduction Zone.
Figure 2
Figure 2. Cross section of the subducting Juan de Fuca Plate. Figure from Vidale, J. and Houston H. (2012) Slow slip: A new kind of earthquake (Physics Today, 2012 pages 38-43).
The last ETS event in Cascadia started in February 2017 around the western edge of the Olympic Mountains. The duration was approximately 35 days with a two-week quiescent period. Prior ETS events in northern Washington/Vancouver Island area was approximately December 2015.
The last ETS event in central Oregon was 2016 and lasted just over a week before it stopped on March 1, 2016.
ETS events are still being studied to understand the processes about slow slip and megathrust earthquakes.
More information about slow slip and tremor can be found here on the PNSN website.